Field of the Invention
The present invention is a mixing device suitable for mixing and applying two component polyurethane foam formulations.
Introduction
Two component polyurethane (2CPU) foam formulations are typically applied by feeding an isocyanate component (A-Component) with a polyol component (B-Component) to create a mixture and then spraying the mixture from a dispenser. There are two types of 2CPU foam formulations: frothed and non-frothed. Frothed foam formulations use a gaseous blowing agent (GBA) such as HFC-134 in the A-Component and a both a GBA and liquid blowing agent (LBA) in the B-Component. Frothed foam can be dispensed at low pressures (less than two megaPascals (MPa)) through a static mixer. In contrast, non-frothed 2CPU foam formulations are free of blowing agents in the A-Component and only have LBA in the B-Component. Non-frothed 2CPUs are dispensed at high pressures, typically 5.5-10 MPa and at an elevated temperature. When dispensing non-frothed 2CPU foam formulations the A and B components are mixed and atomized during application by high pressure impinging contact of the two Components. The high pressure accompanied by heating of non-frothed 2CPU foam formulations necessitates expensive mixing and dispensing devices that can tolerate the pressure and temperature requirements.
It is desirable to reduce the necessary pressure for non-frothed 2CPU foam formulations during mixing and application to less than two MPa, thereby eliminating the need for applicators that are robust at pressures in excess of 5 MPa as is typically required.